84cj w/ 350! its damn slow, what gears to use?? - Page 2 - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

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post #11 of (permalink) Old 09-23-2001, 08:30 PM
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Re: 84cj w/ 350! its damn slow, what gears to use??

If that 20 rear is stock with the 2 piece axles then it will break, I broke mine with my 350... but in your drivetrain the t4 might break first... I had a sm465 so the axle was definately the part to go... i ran 3.55's in my 44 with my 350 and kinda wanted a little more gear... so 3.73 or higher would be good....

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post #12 of (permalink) Old 09-26-2001, 02:03 PM
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Re: 84cj w/ 350! its damn slow, what gears to use??

actually, the axles broke first. when i removed the coverplate, the ring and pinion definately looked fukd up. they were chipped to pieces. now for the tranny, the shifter fell about 2 inches into the case. all the syncros wer totaled. i was downshifting pulling into Logan airport and BOOM all at once. what a mess. i had a traffic cop help me push it out of traffic. that was fun. the second tranny came from a broncoII. what a piece of crap! i parted out the scrambler a few months later. Of course my new scrambler is still waiting to see the light of day! 2+ years i had it and it has not moved under its own power yet. i went with a th400/d300 combo to go with the 9"s front and rear. i wont be breaking anything now!!! i ve decide to go with 4.10s for the kid! thanks as always

304/th400/ford 9"s front/back 7"lift 15x10/35's
it will run someday
post #13 of (permalink) Old 09-26-2001, 07:16 PM
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Re: 84cj w/ 350! its damn slow, what gears to use??

that was a joke, wasn't it merunuover?
the 350 MIGHT not break it driving around town, but any kind of serious off-roading and you'd be hearing some snap, crackle, pop.


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post #14 of (permalink) Old 09-27-2001, 01:40 AM
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Re: 84cj w/ 350! its damn slow, what gears to use??

He man , beleive what you want to . This is what I am running and it works . I have greatly increased the strength of the AMC 20 with the detroit and 1 piece shafts . The ring gear is the same size as the infamous 12 bolt GMC axle . You don't get ant stronger than a Detroit plus the new Superior gears . Like I said before I have 39.5 in tall by 18 inch wide Super Swamper Boggers . The AMC 20 takes all of them with the 282 HP and 301 LB FT of torque at the rear wheels . I have taken my jeep in the mountains at Fort Huachuca which blows away any trail you have heard about . This includes the Rubicon and the others covered in the magazines . Don't even dare take a rig with smaller than 38's up there and ahuge lift . The Huachuca mountains in Arizona are no joke . You have never heard of these but myself being in the military was bless with some bad ass fourwheelin . No mud of course but rocks galore . Personally I think rock crawlin is boring but to each his own . It tears up your tires and cuts the sidewalls . Just imagine this to a set of $330 a piece tires . I also ran 33's with no AMC 20 mods to the axle , help up fine . I stripped the stock two piece splines with the 39.5 inch Boggers though on the street . I figured a $300 upgrade for one piece axles was worth the price VS. $4-$5,000 for a custom Dana 60 by the time you have it setup and running . No doubt the Dana 60 is stronger than the AMC 20 but not $4000 stronger , sorry .

post #15 of (permalink) Old 09-27-2001, 02:38 AM
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Re: 84cj w/ 350! its damn slow, what gears to use??

OK, "run over" let's say the guy has a mild 350 (200hp, 300ft/lbs) In first-low with the t-4 and the 300 with the 4.10's they are talking about putting in you get a total torque multiplication(less a 10% loss for drivetrain drag) of over 11,000 ft/lbs at the axleshafts at peak torque. That's a lot of oomph on a 1.250" axleshaft. Almost 2900 ft/lbs at the pinion stem and pushing the teeth of the ring and pinion. The 20 is a pretty good axle, but thats a lot of load. Especially if it takes a bounce and goes through a loaded-unloaded-loaded cycle.

The 12 bolt GM made it's reputation in muscle cars, not 4wd's. It never saw the loads a built 4x4 sees. It is a great axle for it's use, but that doesn't mean a 20 is bulletproof because they have the same ring gear dia. Guys who wheel GM trucks swap out their 12 bolts (which have a smaller pinion stem than the car version) for 14 bolts, 60's, and 70's.

From what little you have in your profile and in your posts it sounds like you have a pretty decent rig, and the fact that your 20 has lived so long is a testament to how tough a 20 really is. But if you wheel it as hard as you say you do (much harder than any of us "lightweights" here to hear you tell it) it is only a matter of time before that 20 is going to give it up. I'm surprised it has lived very long at all turning 40's. Better start saving up friend, your gonna need one of those "$4000 dollar" Dana 60's. If you stick around on this board, and lighten up a little, you may learn how build your own 60 for quite a bit less.

September 11, 2001- We will not forget! We will not forgive!
post #16 of (permalink) Old 09-27-2001, 07:39 AM
 
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Re: 84cj w/ 350! its damn slow, what gears to use??


... lets not forget the "common sense of the pilot" factor, that can influence to a great extend the life and death of ANY axle...

;o)

Alfred

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post #17 of (permalink) Old 09-27-2001, 10:36 AM
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Re: 84cj w/ 350! its damn slow, what gears to use??

Since merunover has a AMC20 is god story ill follow it up with its a horrible horrible piece of [censored] story.... So I had a 2.5L stock straight 4... damn thing shouldnt even be called an engine... I am driving just on the street from school... not dogging on it or anything and never did in the 2 years I owned it... and bam... lose the axle... so a sub 100 hp engine turning 33s can break the AMC20... did I fix it? NOPE, did I build it up so it can handle 40's so I can break it in the future? NOPE... I threw it away and dropped in a D44 for the massive price of $200....

post #18 of (permalink) Old 09-27-2001, 06:07 PM
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Re: 84cj w/ 350! its damn slow, what gears to use??

Has anyone heard the "snap,crackle,pop" from the breaking of a ONE piece AMC20?

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